Before various articles can be made from tobacco leaves, it is necessary to clean the leaves to remove dust and other contaminants from them. Prior to processing, tobacco leaves are subjected to a wide variety of contamination from insects, dust, sand and the like. In addition, the leaves of flue-cured tobacco are tied together and looped onto tobacco sticks with cotton string which supports the leaves in the curing barns during the curing process. Frequently, these cotton strings or portions of the strings become mixed in with the leaves during the subsequent processing operations.
Tobacco scraps and some tobacco leaves also are packed in burlap sacks for delivery from the growers to the processing plants; and when tobacco scraps and leaves are emptied from such burlap bags, burlap fibers become mixed in with the leaves and scraps of tobacco. A variety of other foreign matter also frequently is present.
Because of the presence of foreign matter in the tobacco leaves and tobacco scraps, the tobacco in a typical processing plant is placed on tables and moved on conveyors past operators who manually pick out the largest and most obvious contaminants, such as string segments, feathers, straw and the like. It is difficult, however, if not impossible, for such operating personnel to remove fine particles such as burlap bag fibers and cotton string fibers and similar contaminants from the tobacco; so that these smaller contaminants are overlooked.
To remove contaminants such as dust, string fibers, insect eggs and the like from the tobacco, tobacco cleaning machines have been developed using rotating brushes for engaging the tobacco leaves as they move on a carrier beneath the brushes. Two such tobacco cleaning machines are disclosed in the Patents to Spierer U.S. Pat. No. 973,228 and Fonseca U.S. Pat. No. 1,831,953. The devices of these two patents are somewhat similar to one another. Each of them employs a carrier to move the tobacco leaves into contact with rotating brushes to engage the surfaces of the leaves to remove strings, dust, insects, larva, eggs and other surface impurities from the tobacco. In Fonseca, the carrier is in the form of a relatively large drum, having a perforated surface and subjected to a partial vacuum to hold the leaves on the drum surface. The drum is rotated beneath rotating cleaning brushes which operate with a type of scrubbing action to remove the contaminants from the leaf surface.
In the machine disclosed in the Spierer U.S. Pat. No. 973,228, the tobacco leaves are carried on an endless belt conveyor in the form of strings which retain the leaves. The leaves then are moved past cleaning brushes which rotate in a direction opposite to the direction of movement of the leaves for dislodging contaminants from the surfaces of the leaves.
A rotating brush machine for cleaning tobacco scrap to separate the tobacco scrap from dirt and larger contaminants is disclosed in the Patent to Skinner U.S. Pat. No. 2,942,607. The machine of the Skinner patent employs a plurality of rotating brushes for moving the tobacco from a hopper up a series of inclined planes to separate the desired tobacco scraps from different sizes of contaminants in various stages of operation. Strings, burlap scraps and the like are intended to be removed by engaging them in the brushes and winding them onto the rotating brushes.
It has been found, however, that even when rotating brush cleaning machines of the type described above are used to remove foreign matter from tobacco leaves, the cleaned tobacco still includes fine particles of lint, string and the like. These particles ultimately become incorporated into the products made from the tobacco. While cleaning machines of the type disclosed in the patents described above do operate to remove a fairly large amount of contaminants from the tobacco leaves, a significant amount of contaminants still remain on the leaves and intermingled with them up to and through the final processing steps.
Consequently, it is desirable to provide a device which can be used to more effectively remove particles of lint, burlap bag fibers, string and other contaminants from tobacco leaves prior to the final processing of such leaves into various products. It further is desirable for such a device to be efficient in operation and inexpensive to manufacture, install, and maintain.